Block V - Cardiovascular Flashcards
12. Electrical activity of the heart 13. Mechanical activity of the heart 14. Blood flow and microcirculation 15. Vessel regulation
Where is the bicuspid or mitral valve located?
The bicuspid valve is located between the left atrium and left ventricle
What is an ECG?
An illustration of the cardiac conduction system
What causes the P wave in an ECG pattern?
Depolarization of atrial muscle fibers
In an ECG, during which wave does ventricular repolarization occur?
T wave
Can ECG be used for determining a patient’s cardiac output stroke volume heart sounds end-diastolic volume?
No. Would be useful for determining heart rate.
What is most responsible for the plateau of the cardiac action potential?
Both calcium and potassium channels
Which cells have pacemaker potential?
The sino-atrial nodal cells
What determines cardiac outpout?
Stroke volume multiplied by heart rate
What is the ratio of stroke volume and end-diastolic volume?
Ejection fraction
Are the stroke volume, stroke work, cardiac output, cardiac work the indices of ventricular performance?
Yes
What is the most important factor in influencing the amount of blood pumped by the ventricle?
Venous return
Which two great vessels bring deoxygenated blood back to the heart?
Superior and inferior vena cavae
When does the first heart sound occur?
The first heart sound occurs during the phase of isovolumetric contraction
What is the correct sequence for the path of cardiac impulse?
SA node, AV node, bundle of His, Purkinje fibers
Where are the bundle of His and its branches located?
The bundle of His and its branches are located in the inter ventricular septum
What are most responsible for phase 0 of a cardiac action potential?
Sodium channels
What events cause cardiacmyocyte repolarization?
Calcium channels begin to close while more potassium channels open; potassium rapidly leaves the cell
What relationship is defined by Frank-Starling’s law of the heart?
End-diastolic volume and stroke volume
The opening of which channel in the auto rhythmic cell (pace maker cell) is responsible for the huge positive spike in membrane potential?
L-type calcium channel
What is the typical stroke volume for an adult at rest?
70 or 80 mL
Which two heart chambers pump oxygenated blood?
Left atrium and left ventricle
When does the atrial systole occur
Towards the end of ventricular diastole
Due to what event does the second heart sound occur?
Closing of the semilunar valves
What is the heart rate dependent on?
Rate of pacemaker potential
Which structure has the slowest conduction velocity of the cardiac impulse?
AV nodal fibers
What is the correct sequence for the blood flow in the heart?
Right atrium, tricuspid valve, right ventricle, pulmonic valve, pulmonary circulation, left atria, mitral valve, left ventricle, aortic valve, aorta
What is the result from delay of spread of electrical activation from atria to ventricles?
The delay allows atrial contraction to push an additional amount of blood into the ventricle before it contracts
Which heart valves open during the diastole and systole of the heart cycle?
Diastolic: AV valves open and semilunar close.
Systolic: AV close and semilunar open
What changes in the ventricular pressure during isovolumic contraction phase of cardiac cycle?
The beginning of ventricular contraction causes leaflets of the mitral valve to close, continuation of ventricular muscle contraction will increase ventricular pressure very rapidly until it exceeds aortic pressure
What is the Beta adrenergic effect on the ventricular myocyte’s function?
It increase cAMP/PKA signal pathway which activates L-type calcium channels. Also, it causes release of free Ca from the SR. The general result is to increase muscle contractility
What is the effect of activation of the baroreceptor reflex during hemorrhage?
Increase in HR due to activation of sympathetic tone on the vasculature
If the systolic arterial pressure is 125 and the diastolic is 85, what is the estimated mean arterial pressure?
98 (diastolic + delta/3)
What is the effect of nitric oxide on vascular smooth muscle cell function?
NO contributes to arteriolar vasodilation in the basal state
What is active hyperemia?
Increasing blood flow of an organ when its metabolic activity increases
Where does the slowest velocity of blood flow occur?
Capillaries
What happens to the capillary hydrostatic pressure when arteriolar constriction occurs?
Decrease
Where does the highest vascular resistance in the cardiovascular system occurs
Arterioles, where the large decrease in pressure within the systemic circulation takes places
What is the effect on HR by decreasing parasympathetic stimulation?
HR increases
What mechanism by which the exchange of lipid-soluble substances (CO2, O2) across the capillary membrane occur?
Diffusion
How do you determine resistance to flow in a BV?
R increases in proportion to the length decreases with 4th power of the radius, increases with viscosity
What will cause a decreases hematocrit in the microcirculation?
The parabolic velocity profile in arterioles and venues with velocity higher near the center of the vessel; deformable RBCs tend to be found closer to the center and away from arteriolar walls; plasma near the wall moves more slowly
Is flow in microcirculation assumed to be steady
Yes
Where is NO released from
Arteriolar endothelial cells
What does the Starling’s Law of Filtration predict?
- less filtration if tissue hydrostatic pressure increases
- more filtration if plasma osmotic pressure decreases
- less filtration if filtration coefficient decreases
Is blood composed of approx. the same number of RBCs and WBCs?
No. RBC are 45% of blood volume while WBC are < 1%
What types of cells are in the microvessel other than hematic cells?
ECs, pericytes, SMCs
What is the myogenic and metabolic vasodilator hypotheses of auto regulation?
Myogenic autoregulation depends on stretch activated ion channels in vascular smooth muscle that, when stretched, allow Ca ions to enter and induce contraction. Metabolic autoregulation is thought to be due, in part, to substances produced in the tissue, in proportion to metabolism, which are vasoactive
What is the Fahraeus effect?
More RBC in arterioles than capillaries
What percent of blood is carried by capillaries?
At any given moment, 5% of circulating blood volume
How close are cells from a capillary?
Most not more than 0.1mm
What is the effect of venous constriction on the capillary hydrostatic pressure?
Increased
What is the relationship between the arteriolar vasodilators production and the local oxygen level?
The production of vasodilators is inversely proportional to the local O2 levels
Does EC produce more NO in response to shear stress?
Yes
What is the effect of sympathetic stimulation on capillary hydrostatic pressure?
Decreased
What factors determine changes in mean arterial pressure?
Cardiac output and/or total peripheral resistance
Does parasympathetic stimulation control arteriolar resistance?
No or minimal
How does a long-term regulation of BP by kidney occur?
It regulates blood volume by adjust salt and water excretion
What is flow auto regulation?
Maintaining blood flow nearly constant in the face of pressure change
What vascular region has the least smooth muscle?
Capillaries
What is the most important factor for vascular resistance?
Diameter
What are the nonadrenergic, noncholinergic autonomic neurons?
A 3rd subsystem of neurons that use NO as a neurotransmitter have been described and found to be integral in autonomic function, particularly in the gut and the lungs
Where is the most blood in the cardiovascular system?
Veins
How does the vasodilator production relate to local O2 level?
Inversely proportional to
Are ECs involved in the myogenic response?
No
